Voltage Glitch Detection In Integrated Circuit

ABSTRACT

An integrated circuit for hardware security comprises a voltage glitch detection processing system comprising an oscillator circuit that generates and outputs a local oscillator clock which is a function of a supply voltage; a counter clocked by the oscillator circuit to generate at least one count value; and a capture section that synchronizes the at least one count value into a system clock domain for detecting a voltage glitch in the supply voltage.

FIELD

The present disclosure relates generally to security protection in dataprocessing systems, and more specifically to supply voltage glitchdetection technology for protecting against fault attacks in a devicecomprising integrated circuits.

BACKGROUND

Data processing systems, such as automotive controller chips, set-topbox systems, chip cards, and other System-on-Chip (SoC) circuits, areincreasingly prone to supply voltage glitch attacks, for example, whichcan include positive or negative voltage glitches to reach or processstored data. One prominent hacking technique is a so-called glitchattack whereby a voltage spike is applied. This may cause transistors ofan integrated circuit (IC) of the chip to switch states in anundesirable and unpredictable manner. For example, a voltage glitchapplied to the supply voltage may temporarily shift the thresholdvoltages of the transistors or logic gates, causing the logic of theembedded central processing unit (CPU) to “skip” instructions andsubsequently cause the CPU to ignore certain safety checks in thesoftware executed by the CPU so that the hacker can take control ofportions of the logic, hijack data before it is encrypted, obtaininformation regarding device architecture, and so on.

One common approach for detecting voltage glitches is to connect ananalog detector such as a voltage sensor to the chip's voltage supplylines. However, they are not easily portable to other process nodes,such as a 16 nm FinFET process, which render the integration of analogsensor systems more difficult.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by way of example and is notlimited by the accompanying figures, in which like references indicatesimilar elements. Elements in the figures are illustrated for simplicityand clarity and have not necessarily been drawn to scale.

FIG. 1 is a block diagram of a computer chip, in accordance withselected embodiments of the present disclosure.

FIG. 2 is a block diagram of a voltage glitch detector, in accordancewith selected embodiments of the present disclosure.

FIG. 3 is a set of timing waveforms illustrating different phases of asynchronization process performed by the voltage glitch detector ofFIGS. 1 and 2, in accordance with selected embodiments of the presentdisclosure.

FIG. 4 is a block diagram of another voltage glitch detection processingsystem, in accordance with selected embodiments of the presentdisclosure.

FIG. 5 is a set of timing waveforms illustrating different phases of asynchronization process of the voltage glitch detector of FIG. 4, inaccordance with selected embodiments of the present disclosure.

FIG. 6 is a block diagram of an automotive microcontroller including avoltage glitch detector, in accordance with selected embodiments of thepresent disclosure.

FIG. 7 is a flowchart illustrating a method for detecting and preventingglitch attacks on a data processing system, in accordance with selectedembodiments of the present disclosure.

DETAILED DESCRIPTION

To address the abovementioned deficiencies and other drawbacks of modernglitch detectors known to those skilled in the art, embodiments of thepresent inventive concept include a security detection system,apparatus, and method that use standard cells in a digital core of acomputer chip, or integrated circuit (IC) or the like, for providingcontinuous protection against voltage or related power or supplyglitches. The glitch detection mechanism overcomes the problemsexperienced by conventional analog glitch sensors with respect toportability to other process nodes by providing a synthesizable detectorconstructed entirely from various electronic logic functions availablein any standard cell library, and which can be applied in the digitaldesigns of different chip types for embedding in a logic block.

In addition, the inventive security detection system, apparatus, andmethod provide greater scalability as well as a greater resolution overconventional glitch detection systems because a ripple counter isconfigured to receive a direct clock. Conventional glitch detectionsystems, on the other hand, typically rely on a delay line formed ofinverters or buffers or related fixed delay logic elements that output aresult to capture flip-flops, and arranged to compensate for unstableinput signals. However, they consume valuable circuit level areas of anintegrated circuit (IC). For example, a delay line can be used todetermine whether a variation exists between the time when the signalshould be stable and when it is actually captured, in particular, bymeasuring the delay of the signal traveling through the logic gates ofthe delay line. The delay line must be long enough to cover at least oneclock cycle of the applied clock, which requires a substantial physicalarea of the detector. In addition, conventional delay-line based glitchdetectors require a corresponding increase in the length of the delayline in order to perform glitch detection with a smaller clockfrequency. For example, a clock reduction from 96 MHz to 12 MHz requiresan increase in the size of a delay size by a factor of 8, which isundesirable in modern chip design where an emphasis is made on reducinglogic elements. The additional logic required for the delay linesconsumes valuable resources of the chip. These resources limit the chipwith respect to additional scaling, clock rate increases, or otherdesired chip improvements.

In addition, the inventive security detection system, apparatus, andmethod offer an automatic adaptation to changed environmental conditionsusing programmable margin settings, by maintaining detection margins assmall as possible and detecting glitches that are not visible ascompared to conventional analog and digital glitch detection systems. Inparticular, typical analog glitch detection mechanisms are constructedand arranged to detect voltages above or below a threshold voltagelevel. The voltages levels are defined by maximum and minimum allowedsupply voltage levels (plus margin). Here, a glitch having voltage belowthis level cannot be detected. The inventive security detection system,apparatus, and method can detect a glitch which exceeds the currentreference plus/minus the margin. The related voltage level can bebelow/above of the levels that the analog sensor would otherwisetrigger. In some embodiments, the inventive security detection system,apparatus, and method automatically adapt to temperature and voltagechanges and maintain a measurement range in an optimal position toprovide increased sensitivity in glitch detection.

Taking into account the degradation of a voltage glitch travelingthrough a computer chip due to the capacity on the power supply grid,the inventive system requires fewer glitch detectors to protect aparticular security critical IC area of interest.

Accordingly, voltage glitch detectors in accordance with embodiments ofthe present inventive concepts can be constructed and arranged forvarious automotive, government, and industrial applications wheresecurity features are required, for example, a chip-based automotivehardware security engine or related security subsystem that requireson-chip security features to prevent illicit access by a hacker, who mayattempt to control an operation of a vehicle via the chip.

FIG. 1 is a block diagram of a computer chip 10, in accordance with someembodiments. The chip 10 may include a set of electronic circuits suchas transistors or other combinations of components formed of metal,oxide, silicon, and so on. The chip 10 may include a processor core,memory, input/output (I/O), and peripheral components (not shown) thatreceive a direct supply voltage from a power source such as other ICs,and can be implemented in various automotive, industrial, and consumerapplications, for example, described with respect to FIG. 6 herein.

The chip 10 may include at least one supply voltage glitch detectionprocessing system 100 and at least one digital circuit 12. The voltageglitch detection processing system 100, also referred to as a voltageglitch detector, can be embodied with the digital circuit 12 as part ofa System-on-Chip (SoC) device or related computer chip in accordancewith selected embodiments of the present disclosure. The digital circuit12 may include various electronic components such as a combination oflogic gates (e.g., AND, OR, and XOR gates), flip-flops, and so onavailable at a standard cell library. In some embodiments, the digitalcircuit 12 may include a post-processing section that includes an errordetection system for generating an alert, event, or error signal when anundesirable glitch is detected.

The voltage glitch detection processing system 100 can likewise beformed from elements of a standard cell library. The voltage glitchdetection processing system 100 is constructed and arranged to performglitch detection functions, including filtering and removing undesirablevoltage glitches with respect to input signals received by the digitalcircuit 12, but in a manner that allows for easy scalability to thesystem clock frequency as compared to a conventional glitch detector. Inparticular, the voltage glitch detection processing system 100 requiresfewer digital logic cells forming the delay line than a conventionalglitch detector while reducing the overall area of the hardwarecomponents of the voltage glitch detection processing system 100. Also,there is a reduced area dependency on the clock frequency. Delay linesoffered by conventional glitch detectors, on the other hand, require ascaling of the delay line length, and therefore an increase in thedetector size, linearly with the clock period. The inventive glitchdetection processing system 100 only requires a scaling of the ringoscillator depending on the resolution of the detector. The area size isalso reduced due to the directly clocked counter and no requirement foran initial delay line.

This reduction can also improve the resolution of glitch detection andautomatically adapt to environmental conditions such as temperaturechanges, noise conditions, and so on because a glitch will experienceless degradation traveling through the chip 10 due to the power supplygrid. The voltage glitch detection processing system 100 relies oncounters rather than delay lines and capture values for glitchdetection, thereby requiring fewer logic components such as delayelements and offering additional advantages over conventional glitchdetection systems as described herein. In some embodiments, the countvalues output from the ripple counter are output to a post-processingsection of the IC that includes an error detection system or the like(not shown), which compares the captured count values against a computedreference value to generate an error signal if the difference betweenthe result, i.e., count value, and the reference value exceeds aprogrammable and predetermined margin value. The reference is calculatedbased on the highest and smallest result, i.e., the count value during agiven time period as determined by a programmable counter. By this thereference can be adapted to acceptable changed environmental conditionsas long as the changes fall within an acceptable range, e.g., anincrease in temperature. In some embodiments, the integrated circuit 10comprises a reference adaption function, wherein the reference value isadapted in a regular time interval to an average of the count valuesreceived in a last time interval.

The abovementioned scalable resolution is achieved because the glitchdetector 100 includes a ripple counter configured to receive a directclock. A single bit added at the ripple counter and post-processinglogic can double the resolution of the glitch detector. For example, theaddition of a single flip-flop is required to increase the detector'sresolution by a factor of 2. Conventional detectors, on the other hand,would require a doubling of the number of flip-flops for a comparableincrease in resolution. Accordingly, the resolution offered by theinventive glitch detector 100 can be enhanced in a manner which ensuresthat there is a sufficient measurement range for all process variationsof the fabrication parameters of the integrated circuit to avoid falsepositives.

FIG. 2 is a block diagram of the voltage glitch detection processingsystem 100 of FIG. 1. As illustrated, in some embodiments, the voltageglitch detection processing system 100 comprises a local clockgeneration circuit 202, a clock gate 204, a multi-bit counter 206, andone or more capture flip-flops of a capture section 208. Although thevoltage glitch detection processing system 100 is shown and described inFIG. 1 as a particular implementation, other configurations andimplementations can equally apply.

In some embodiments, the local clock generation circuit 202 comprises anoscillator circuit such as a ring oscillator for clocking the counter206. Although FIG. 2 illustrates a ripple counter 206, other countertypes can equally apply. A local oscillator clock OCK is generated bythe ring oscillator according to a frequency that is dependent on asupply voltage (VDD) provided on a bus or other conduit, line, or thelike to various electrical components of the computer chip 10, which mayhave voltage transients of which glitch detection is performed by thesystem 10. Accordingly, the output OCK of the ring oscillator can beused to clock the ripple counter 206 for a period of time defined by theapplied system clock. The ring oscillator frequency is determined by theconstruction of the oscillator, for example, in turn established by alength of the ring oscillator delay chain. The propagation delay in thering oscillator circuit 202 is output as a function of the supplyvoltage (VDD).

The clock gate 204 is constructed and arranged to stop, or gate, thelocal oscillator clock OCK to allow a count value output from the ripplecounter 206 to settle before being captured into the clock domain of theouter system, or synchronize, since the value may not settle to a stablevalue in a single clock cycle. The value has a direct relationship withthe supply voltage, especially if considered in a regular manneraccording to a fixed time frame defined on the basis of the systemclock. In some embodiments, the clock gate 204 includes an enable input(CLK Enable) provided by clock enable logic input to an AND gate or thelike that controls the clock, for example, by gating the output so thatno clock is output during predetermined periods of the synchronizationprocess, and thereby controlling when the counter 206 increments itsvalue. The foregoing illustrates one possible synchronization technique,but not limited thereto.

In addition, the clock gate 204 can reduce power consumption of thedevice while also allowing a count value output from the ripple counter206 to settle.

The ripple counter 206 is constructed and arranged to receive a gatedclock signal directly from the clock gate 204. As previously mentioned,the ripple counter 206 is clocked by a ring oscillator 202 or the like.Due to the supply voltage dependence by the ring oscillator 202, thecount value in the ripple counter 206 will have a direct relationshipwith the supply voltage (VDD) when the oscillator clock OCK clocks theripple counter 206 for a predetermined period of time defined by thesystem clock, which in turn is generated in a regular manner based onthe fixed time frame, i.e., defined by the period of the clock used inthe system the voltage glitch detection processing system 100 isdesigned to protect. The ripple counter 206 has a reset input forclearing a count value to zero. More specifically, the ring oscillatoroutput is used to clock the ripple counter 206 for a certain period oftime defined by the applied system clock having a static clockfrequency. After each period, the current value of the counter 206 iscaptured, the counter 206 is reset to establish a new period.

The capture section 208 includes one or more capture flip-flopsconstructed and arranged to synchronize a bit level signal, and morespecifically, to capture the count values output from the ripple counter206 with the system clock domain as part of a synchronization process.The output of the capture section 208 can be provided to post-processingsection of the IC, or an external error correction device or the likethat is in communication with the chip 10.

The underlying concept of this invention is to use the subsequent valuesof one or more counters clocked by a voltage dependent clock source,e.g. a ring oscillator clock, sample them in a fixed time frame, e.g.defined by the system clock and to compare the subsequent values againsteach other's by generating a reference value from the count values. Asdescribed herein, a feature of the present inventive concept is tocompare voltage dependent count values captured in a regular timeinterval defined by the system clock. A reference is calculated from thecount values. If a count value exceeds the reference plus a particularmargin, then an error signal is generated. The use of two clock sourcesfor clocking the counters and generating the time reference requires aso-called clock domain crossing between those. One such concept isdescribed as follows.

For an improved understanding of the operation of a voltage glitchdetector described in FIGS. 1 and 2, reference is now made to FIG. 3which illustrates a timing diagram 300 of relevant input and outputsignals from the voltage glitch detector 100.

As shown in FIG. 3, a system clock is provided having a predeterminedfixed frequency. As previously described, the result, or output of thecounter 206, is directly dependent on the supply voltage during the lastmeasurement period, defined by the period the clock gate 204 is open andthe clock of the ring oscillator passes through to the ripple counter.The measurement period is defined by the system clock. Depending on thefrequency relation of the ring oscillator and the system clock someembodiments might use a measurement period of one system clock cyclesother embodiments might use more system clock cycles. The number of thering oscillator clocks in a selected measurement period defines thepossible resolution of the detector. The ripple counter 206 increments astored count value on the clock edge of the gated clock signal. In someembodiments, the gated clock output from the clock gate 204 is providedat the rising edge of the count pulse, and is applied to the count pulseto synchronize the counter value into the clock domain of the system.The clock from the ring oscillator 202 passing through the clock gate204 is applied to the counter 206. This will count as long the clockgate 204 is open. The settle, capture, and result phases of thesynchronization process follow the count phase, but unlike the countpulse, are not dependent on the supply voltage, and therefore notsusceptible to glitches in the supply voltage. In particular, duringsynchronization the clock of the ripple counter 206 must be stopped toallow the count value to settle. After the settling period the countvalue is captured into the system clock domain. Subsequently, the ripplecounter 206 is reset, e.g., an asynchronous reset as shown in FIG. 3.

Since glitch detection is not performed with respect to the clock pulsesof the settle, capture, and reset phases respectively, it follows thatglitch detection does not occur in every system clock cycle. However,turning to FIGS. 4 and 5, a plurality of ripple counters can beconstructed and arranged to allow a voltage glitch detection processingsystem to generate a continuous glitch detection in each clock cycle,and which allow count values to be held in the various stages of thecounting and synchronization processes.

Referring to FIG. 4, a circuit diagram of a voltage glitch detectionprocessing system 400, in accordance with selected embodiments isdescribed. At least some elements of the voltage glitch detector 400 arethe same or similar to those described with respect to the voltageglitch detection processing system 100, thus are not repeated forbrevity.

A clock gate 404A-404D (generally, 404) comprises a plurality of logicgates, for example, AND gates. Each clock gate 404 has an output coupledto a ripple counter 406. Each clock gate 404 has a first inputconstructed and arranged to receive a local oscillator clock OCK from aring oscillator 402 and a second input for receiving a related clockenable signal from a clock and capture control module 410.

The clock and capture control module 510 is constructed and arranged tocommunicate with the clock gates 404 and a selection circuit 412 such asa multiplexer or the like. By means of the clock enable and captureselect signal the selection circuit 412 will control the clock gates ina way that the clock from the ring oscillator 402 is applied to only oneof the ripple counters 406 at a time and that with every system clockthe count value from one ripple counter 406 is captured. FIG. 5 showsthe related timing diagram 500. In particular, the timing diagram 500shows the shifted behavior of the four parallel clock gates 404 andripple counters 406 pairs with the shifted measurement, settle captureand reset phases. The values shown in the diagram are example values toassist in the understanding which count value is being taken over intothe capture flip-flops, 408 referred to herein as Result. The captureselect value defines the counter 406 from which the value is taken overinto the Result in the next rising clock edge. E.g. if Capture select is1, the value from counter 1 is taken over into the Result.

As described above, the output of a voltage glitch detection processingsystem can be provided to post-processing section of the chip 10, e.g.,post-processing section of digital circuit 12, or to an external errorcorrection device or the like that is in communication with the chip 10.The post-processing section can evaluate this output by comparing theripple counter value against a reference value. In particular, thesynchronized count value is compared to the reference value, which inturn is calculated from prior count values. In some embodiments, thereference value may be a fixed value. In other embodiments, as describedbelow, the reference value may be a variable value.

If the difference between reference value and result is bigger than aprogrammable positive margin or smaller than a programmable negativemargin then an error is raised. The programmable margin settings allowthe voltage glitch detection processing system to adapt the differentkind of noise profiles on different chips and applications and to assurean optimum detection rate for glitches while avoiding false positives ornegatives. In some embodiments, this is achieved by the inventivesecurity detection system, apparatus, and method allowing a continuousglitch detection operation to be performed in every system clock cycle,illustrated for example in FIGS. 4 and 5.

Also, digital post-processing can be performed to remove the impact oftemperature and slow supply voltage changes on the result the referencevalue is regularly adapted to the measured result. The update rate canbe programmed via a timer setting. An update timer (not shown) can beprovided that generates a periodic timing reference signal for updatingthe reference value.

For each timer period the highest and lowest measurement result(minimum/maximum) is determined. An average of the maximum and minimummeasurement result can be used for the reference value. At the end ofthe timer period the reference is averaged with these values with aprogrammable weight. Having the weight of reference programmable, allowsto suppress big changes in the reference value due to changes in thesupply noise due to changes in the application. Accordingly, the systemcan offer an automatic adaptation to changed environmental conditionsusing programmable margin settings, by maintaining detection margins assmall as possible and detecting glitches that are not visible ascompared to conventional analog and digital glitch detection systems. Inaddition, the inventive security detection system, apparatus, and methodcan automatically compensate for temperature changes.

As described herein, embodiments of the inventive concept detect voltageglitches by comparing consecutive count values clocked by a ringoscillator that is dependent on a supply voltage. The subsequentlygenerated count value may also depend on the frequency of the systemclock as this determines the length of the measurement period.Accordingly, in some embodiments, the system is constructed and arrangedto operate as a frequency monitor without additional structuralrequirements or changes.

FIG. 6 is a block diagram of an automotive microcontroller 600 includinga voltage glitch detector 620, in accordance with selected embodimentsof the present disclosure. The automotive microcontroller 600 may beimplemented for various automobile functions including but not limitedto automotive radar systems, braking and stability control, electricpower steering (EPS), hybrid and electric vehicle power inverter,powertrain, converter and charger. Although shown in FIG. 6 as part ofan automotive chip, the voltage glitch detector 620 can apply to anychip which requires a protection against supply voltage glitching andwhich contains a synthesized digital logic section. In general, allsecurity related chips, integrated circuits, or the like may includefeatures of the present invention, for example, quantum technologiesimplemented in radio chips provided by the Institute of Defense Analysis(IDA) or other security protection mechanisms.

The voltage glitch detector 620 may be the same as or similar to voltageglitch detectors 100, 400 described in FIGS. 1-5, respectively. Thevoltage glitch detector 620 may be part of a security system 608 andcommunicate with other elements of the automotive microcontroller 600 ona chip, including but not limited to a memory 602, CPU 604, motorcontrol system 606, security system 608, serial communications 610, andinput/output (I/O). The security system 608 in particular is constructedand arranged to provide safety functionality and fault recovery thatdetects, isolates, and resolves computer faults without system shutdown.The security system 608 executing the voltage glitch detector 620 canprovide protection against malicious hacking.

FIG. 7 is a flowchart illustrating a method 700 for detecting andpreventing glitch attacks on a data processing system, in accordancewith selected embodiments of the present disclosure. Some or all of themethod 700 can be performed in a computer chip described in embodimentsherein, for example, performed by a glitch detector hardware engine thatis connected to the supply lines in an appropriate way.

At block 702, an oscillator clock signal is generated that has afrequency that is dependent on the supply voltage of the circuit ofinterest.

At block 704, the oscillator clock signal is used to clock a counter fora predetermined amount of time defined by the applied system clock. Insome embodiments, the counter is a ripple counter. Other embodiments mayinclude other counter types.

At block 706, the counter generates a counter value. Due to the supplyvoltage dependency of the ring oscillator frequency the value in theripple counter has a direct relationship with the voltage if evaluatedin a regular manner based on a fixed time frame. The fixed time frame isdefined by the period of the clock used in the system the detector shallprotect.

At block 708, the ripple counter value is synchronized into the systemclock domain. In doing so, the oscillator clock may be stopped to allowthe value to settle. After settling, the value can be captured into thesystem clock domain.

At block 710, the foregoing is provided to a post-processing computer,such as digital circuit 12 of FIG. 1.

As will be appreciated, embodiments as disclosed include at least thefollowing embodiments. In one embodiment, an integrated circuit forhardware security comprises a voltage glitch detection processing systemcomprising an oscillator circuit that generates and outputs a localoscillator clock, which is a function of a supply voltage; and a counterclocked by the ring oscillator to generate at least one count value; anda capture section that synchronizes the at least one count value into asystem clock domain for detecting a voltage glitch in the supplyvoltage.

Alternative embodiments of the integrated circuit for hardware securityinclude one of the following features, or any combination thereof.

The voltage glitch detection processing system further comprises a clockgate that generates a gated clock from the local oscillator clock tocontrol a receipt by the ripple counter of the local oscillator clock.

The capture section synchronizes the count value into the system clockdomain after a settling period of the count value in response to thegated clock.

The local oscillator clock is stopped to allow the count value to settlein the settling period.

The ripple counter has a reset input for clearing the at least one countvalue to zero.

After each period, a current value of the at least one count value ofthe counter is captured, and the counter is reset to establish a newperiod.

The counter increments the at least one count value on a clock edge ofthe gated clock and the gated clock is output from the clock gate isprovided at the rising edge of a count pulse, and is applied to thecount pulse.

The at least one counter value is directly dependent on the supplyvoltage during a measurement period when the clock gate is open and thelocal oscillator clock passes through the clock gate to the counter, anda resolution of the voltage glitch detection processing system isdetermined by a number of ring oscillator clocks in the measurementperiod.

The integrated circuit further comprises an error detection system,wherein the at least one count value is output from the counter to theerror detection system, which to generates an error signal when the atleast one count value is different than a reference value by apredetermined margin.

The integrated circuit further comprises a reference adaption function,wherein the reference value is adapted in a regular time interval to anaverage of the count values received in a last time interval.

The integrated circuit further comprises a plurality of clock gates,each of the clock gates generating a gated clock to a counter of aplurality of counters in parallel with the clock gates, which generate acontinuous glitch detection in each clock cycle of a system clock.

The integrated circuit further comprises a clock and capture controlmodule that outputs a clock enable signal to the clock gates so that thegated clock in response to the local oscillator clock is applied to onlyone of the counters at a time.

The clock gates are logic AND gates, each having a first input forreceiving the local oscillator clock from the ring oscillator and asecond input for receiving the clock enable signal from the clock andcapture control module.

The integrated circuit further comprises a selector that controls anoutput of the counters so that one count value at a time is captured bythe capture section.

In one embodiment, a voltage glitch detection processing system for aSystem-on-Chip (SoC) device, comprises an oscillator circuit thatgenerates and outputs a local oscillator clock, which is a function of asupply voltage; and a counter clocked by the ring oscillator to generateat least one count value that are synchronized with a system clock todetect a voltage glitch in the supply voltage.

Alternative embodiments of the voltage glitch detection processingsystem include one of the following features, or any combinationthereof.

The voltage glitch detection processing system further comprises a clockgate (204) that controls the local oscillator clock to allow the atleast one count value output from the counter to settle prior to beingcaptured into a domain of the system clock such that the clock value hasa direct relationship with the supply voltage.

The at least one count value of the counter is clocked by the localoscillator clock, sampled in a fixed time frame defined by the systemclock, and compared to subsequent count values.

The voltage glitch detection processing system further comprises aplurality of clock gates, each of the clock gates generating a gatedclock to a counter of a plurality of counters in parallel with the clockgates, which generate a continuous glitch detection in each clock cycleof a system clock.

The system is constructed and arranged to operate as a frequencymonitor.

In one embodiment, a method for detecting a supply voltage glitch attackat a hardware security integrated circuit comprises: generating a firstclock as a function of a supply voltage; generating a count value inresponse to the first clock; and synchronizing the count value into asecond clock domain to detect a voltage glitch in the supply voltage.

Alternative embodiments of the voltage glitch detection processingsystem include one of the following features, or any combinationthereof.

The first clock is a local oscillator clock and the second clock is asystem clock.

Although the invention is described herein with reference to specificembodiments, various modifications and changes can be made withoutdeparting from the scope of the present invention as set forth in theclaims below. Accordingly, the specification and figures are to beregarded in an illustrative rather than a restrictive sense, and allsuch modifications are intended to be included within the scope of thepresent invention. Any benefits, advantages, or solutions to problemsthat are described herein with regard to specific embodiments are notintended to be construed as a critical, required, or essential featureor element of any or all the claims.

Unless stated otherwise, terms such as “first” and “second” are used toarbitrarily distinguish between the elements such terms describe. Thus,these terms are not necessarily intended to indicate temporal or otherprioritization of such elements.

What is claimed is:
 1. An integrated circuit for hardware security,comprising: a voltage glitch detection processing system, comprising: anoscillator circuit that generates and outputs a local oscillator clock,which is a function of a supply voltage; a counter clocked by theoscillator circuit to generate at least one count value; and a capturesection that synchronizes the at least one count value into a systemclock domain for detecting a voltage glitch in the supply voltage. 2.The integrated circuit of claim 1, wherein the voltage glitch detectionprocessing system further comprises: a clock gate that generates a gatedclock from the local oscillator clock to control a receipt by thecounter of the local oscillator clock.
 3. The integrated circuit ofclaim 2, wherein the capture section synchronizes the count value intothe system clock domain after a settling period of the count value inresponse to the gated clock.
 4. The integrated circuit of claim 3,wherein the local oscillator clock is stopped to allow the count valueto settle in the settling period.
 5. The integrated circuit of claim 4,wherein the counter has a reset input for clearing the at least onecount value to zero.
 6. The integrated circuit of claim 5, wherein aftereach period, a current value of the at least one count value of thecounter is captured, and the counter is reset to establish a new period.7. The integrated circuit of claim 2, wherein the counter increments atleast one count value on a clock edge of the gated clock and the gatedclock is output from the clock gate is provided at the rising edge of acount pulse.
 8. The integrated circuit of claim 2, wherein the at leastone counter value is directly dependent on the supply voltage during ameasurement period when the clock gate is open and the local oscillatorclock passes through the clock gate to the counter, and wherein aresolution of the voltage glitch detection processing system isdetermined by a number of oscillator clocks in the measurement period.9. The integrated circuit of claim 1, further comprising an errordetection system, wherein the at least one count value is output fromthe counter to the error detection system, which to generates an errorsignal when the at least one count value is different than a referencevalue by a predetermined margin.
 10. The integrated circuit of claim 9,further comprising a reference adaption function, wherein the referencevalue is adapted in a regular time interval to an average of the countvalues received in a last time interval.
 11. The integrated circuit ofclaim 1, further comprising a plurality of clock gates, each of theclock gates generating a gated clock to a counter of a plurality ofcounters in parallel with the clock gates, which generate a continuousglitch detection in each clock cycle of a system clock.
 12. Theintegrated circuit of claim 11, further comprising a clock and capturecontrol module that outputs a clock enable signal to the clock gates sothat the gated clock in response to the local oscillator clock isapplied to only one of the counters at a time
 13. The integrated circuitof claim 12, wherein the clock gates are logic AND gates, each having afirst input for receiving the local oscillator clock from the oscillatorcircuit and a second input for receiving the clock enable signal fromthe clock and capture control module.
 14. The integrated circuit ofclaim 12, further comprising a selector that controls an output of thecounters so that one count value at a time is captured by the capturesection.
 15. A voltage glitch detection processing system for aSystem-on-Chip device, comprising: an oscillator circuit that generatesand outputs a local oscillator clock which is a function of a supplyvoltage; and a counter clocked by the oscillator circuit to generate atleast one count value that are synchronized with a system clock todetect a voltage glitch in the supply voltage.
 16. The voltage glitchdetection processing system of claim 15, further comprising a clock gatethat controls the local oscillator clock to allow the at least one countvalue output from the counter to settle prior to being captured into adomain of the system clock such that the clock value has a directrelationship with the supply voltage.
 17. The voltage glitch detectionprocessing system of claim 15, wherein the at least one count value ofthe counter is clocked by the local oscillator clock, sampled in a fixedtime frame defined by the system clock, and compared to subsequent countvalues.
 18. The voltage glitch detection processing system of claim 15,further comprising a plurality of clock gates, each of the clock gatesgenerating a gated clock to a counter of a plurality of counters inparallel with the clock gates, which generate a continuous glitchdetection in each clock cycle of a system clock.
 19. The voltage glitchdetection processing system of claim 15, wherein the system isconstructed and arranged to operate as a frequency monitor
 20. A methodfor detecting a supply voltage glitch attack at a hardware securityintegrated circuit, comprising: generating a first clock as a functionof a supply voltage; generating a count value in response to the firstclock; and synchronizing the count value into a second clock domain todetect a voltage glitch in the supply voltage.